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Warmup Tuesday 11/29

Warmup Tuesday 11/29. 1) Define each term in your own words: Wavelength: Wave period:. Wind blowing across water tries to drag the water with it, Ripples – form first:. Things that affect how big waves get. Speed of wind : Faster wind makes bigger waves! (duh)

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Warmup Tuesday 11/29

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  1. Warmup Tuesday 11/29 1) Define each term in your own words: Wavelength: Wave period:

  2. Wind blowing across water tries to drag the water with it, Ripples – form first:

  3. Things that affect how big waves get Speed of wind : Faster wind makes bigger waves! (duh) Duration of wind : longer time blowing = bigger waves! FETCH of the wind : if the wind blows over a large part of the ocean = bigger waves

  4. “Fully developed seas”Largest waves for that winds speed, duration, & fetch

  5. Swells – even waves, left the “cause” area, now just rolling away

  6. From Seas to Swell Beyond the fetch, wave groups Are sorted out due to dispersion Fetch Seas Ocean swell Wave profile Waves of various periods and heights are generated in the fetch. The chaotic wave profile in this region is referred to as “seas”. Longer period waves propagate away from the fetch and may disperse across 1000s of km as smoother, more uniform ocean “swell”.

  7. This wave was not “cause” here

  8. Period – How much time between each crest? • Physical Traits Frequency – How many crests pass each second?

  9. Wave Anatomy • Physical Traits

  10. Water does not move forward, just the energy “wave” http://faculty.gvsu.edu/videticp/wave_animation1.GIF

  11. Particle Motion in a Deep Water Wave L H L 2 • Physical Traits - At the surface, orbital diameter equals the wave height H. - Orbital diameter decreases with depth - At a depth of L/2, motion is negligible Animation from: Dan Russell, Ph.D., Associate Professor of Applied Physics at Kettering University in Flint, MI 3D Simulator http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html http://www.kettering.edu/~drussell/Demos/waves-intro/waves-intro.html

  12. http://www.forgefx.com/casestudies/prenticehall/ph/waves/waves.htmhttp://www.forgefx.com/casestudies/prenticehall/ph/waves/waves.htm

  13. Wave energy reaches down to 0.5 the wavelength of a wave.

  14. Example: A storm generates waves that are 100ft tall and 200 ft in wavelength. How far down will a fish have to be to NOT feel these big waves?

  15. Wave Trains/ wave interference Two waves Animation from: Dan Russell, Ph.D., Associate Professor of Applied Physics at Kettering University in Flint, MI Two waves traveling in the same direction. The waves alternate between constructive and destructive interference. This is very common on beaches! You’ll see 4-6 large waves, 4-6 small waves, repeat!! Because the waves you see are a sum of multiple wave patterns all combined together.

  16. Wave trains In this animation two sine waves in deep water with periods of 9.2 and 10.0 seconds, respectively, are superimposed to form the wave group. Note the pattern of wave groups separated by regions of calm. Observe that the individual waves travel faster than the groups. If you try to follow an individual wave crest you will see that it disappears. However, if you follow a group you will see that it continues to persist. It travels clear across the screen.

  17. FYI: Waves to electricity!

  18. Shallow water wave Particle Motion Deep Water Wave (h / L >= ½) Circular Decreasing With Depth L Shallow Water Wave (h / L =< 1/20) Elliptical Near Surface Flatter With Depth Intermediate Wave (1/20 < h / L < ½) Elliptical Decreasing & Flatter With Depth H h

  19. Wave Shoaling Wave’s slow down and squish together Speed and wavelength decrease BUT!!! Wave period remains constant!

  20. Wave Shoaling In shallow water with beaches of mild slope, waves break when their height is approximately 78% of water depth For our calculations, lets round that down to 75%!!!

  21. So… if a wave crashes when its wave height is 75% of the water depth… • At what water depth will a 20ft wave crash? • You see 8 ft waves crashing… so how deep must it be right there? • Or, it is 10ft deep when a wave crashes… how height was the wave?

  22. Wave Shoaling Types of Breakers Tidal Modulation of Surf Zone For a given wave height, bottom depth determines where the waves break. For a given wave steepness, bottom slope determines how they break.

  23. Summary • Three things affect the height of waves: • The water has no “net” movement in waves, the water particles in a wave move in a circle - • Deep water waves are waves in water greater than ½ their wavelength (NOT wave height). • The energy of a wave reaches down to ½ it’s wavelength. • Waves “break” when their wave height is 75% of the water depth. • Wave motion in shallow water is more of a “back and forth” than a circle.

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